Paul McCartney has become the latest celebrity to reach out to NASA, urging the agency not to use monkeys in radiation experiments to determine its effect on humans.

“I believe NASA has the ingenuity to investigate the health effects of space travel without confining and experimenting on animals as was done in the old days,” McCartney wrote, reports Gigwise.

“It would be terribly disappointing if in our zeal to explore new frontiers and to learn about the fascinating universe where we live we began to regress in our treatment of the animals with whom we share this planet.”